Stenting has become an increasingly important treatment option for patients with coronary artery disease. Stenting involves the placement of a tubular prosthesis within a diseased coronary artery to expand the arterial lumen and maintain the patency of the artery. Early stent technology suffered from problems with restenosis, the tendency of the coronary artery to become re-occluded following stent placement. However, in recent years, improvements in stent design and the advent of drug-eluting stents have reduced restenosis rates dramatically. As a result, the number of stenting procedures being performed in the United States, Europe, and elsewhere has soared.
Stents are delivered to the coronary arteries using long, flexible vascular catheters typically inserted through a femoral artery. For self-expanding stents, the stent is simply released from the delivery catheter and it resiliently expands into engagement with the vessel wall. For balloon expandable stents, a balloon on the delivery catheter is expanded which expands and deforms the stent to the desired diameter, whereupon the balloon is deflated and removed.
Current stent delivery technology suffers from a number of drawbacks. For example, current stent delivery catheters are not capable of customizing the length of the stent in situ to match the size of the lesion to be treated. While lesion size may be measured prior to stenting using angiography or fluoroscopy, such measurements may be inexact. If a stent is introduced that is found to be of inappropriate size, the delivery catheter and stent must be removed from the patient and replaced with a different device of correct size.
Moreover, current stent delivery devices cannot treat multiple lesions with a single catheter. Current devices are capable of delivering only a single stent with a single catheter, and if multiple lesions are to be treated, a new catheter and stent must be introduced for each lesion to be treated.
Further, current stent delivery devices are not well-adapted for treating vascular lesions that are very long and/or in curved regions of a vessel. Current stents have a discrete length that is relatively short due to their stiffness. If current stents were made longer so as to treat longer lesions, they would not conform well to the curvature of vessels or to the movement of vessels on the surface of the beating heart. On the other hand, any attempt to place multiple stents end-to-end in longer lesions is hampered by the inability to maintain appropriate inter-stent spacing and to prevent overlap of adjacent stents.
Many of the above shortcomings are addressed by various currently pending patent applications assigned to the assignee of the present application, such as U.S. patent application Ser. Nos. 10/306,622, filed Nov. 27, 2002; 10/306,620, filed Nov. 27, 2002; 10/306,813, filed Nov. 27, 2002; 10/412,714, filed Apr. 10, 2003; 10/637,713, filed Aug. 8, 2003; 10/624,451, filed Jul. 21, 2003; 10/738,666, filed Dec. 16, 2003; 10/458,062, filed Jun. 9, 2003; 10/686,507, filed Oct. 14, 2003; 10/686,025, filed Oct. 14, 2003; 10/687,532, filed Oct. 15, 2003; 10/46466, filed Dec. 23, 2003; and 10/794,405, filed Mar. 3, 2004, all of which are hereby incorporated fully by reference. Although many improvements in stent design and stent delivery techniques have been suggested, improvements are still being sought.
For example, repair of vessels at areas of bifurcation is particularly challenging. A bifurcation of a vessel is generally a division into two branches, such as a main branch and a side branch. Generally, treatment of such bifurcated vessels with stents is difficult because it is technically challenging to place one or more stents in a main vessel and one or more stents in a branching vessel so as to sufficiently treat the existing lesion(s) while not interrupting blood flow through either the main or branch vessel. Oftentimes, if the main vessel is treated sufficiently with a stent, the stent disrupts flow into the branching vessel and/or makes placement of additional stents in the branching vessel quite difficult. In other cases, placement of a stent in the branching vessel may hinder stent placement and/or blood flow in the main vessel. Difficulties in stent-based treatment of bifurcated vessels occur due to limitations of both current stent designs and currently available stent delivery devices and techniques.
Some currently available systems for placing stents at an area of vessel bifurcation require placement of a first stent in one branch of the vessel, removal of the catheter from the body, insertion of a second catheter to place a second stent, and so on until a desired number of stents is placed. Other available techniques involve insertion of two catheters simultaneously to place stents in two branches of a bifurcated vessel. A number of other alternative techniques and devices have been developed for treating vessel lesions at bifurcations. Some methods are described, for example, in U.S. Pat. Nos. 6,033,434 and 6,582,394, as well as PCT Patent Application Publication No. WO 2004/017865.
All of these currently available devices and methods for delivering stents at vessel bifurcations have one or more drawbacks. Perhaps most obvious is the inconvenience and additional time and expense of using multiple catheters to place multiple stents in the bifurcated vessel. As discussed above, currently available devices and methods also do not provide for placement of custom length stents.
For these and other reasons, stents and stent delivery catheters are needed which facilitate treatment of vessels at areas of bifurcations. Ideally, such stents and delivery catheters would allow for placement of stents in a main vessel and a branch vessel, without requiring removal of the delivery catheter from the patient. Also ideally, customization of stent length in situ would be provided, as well as treatment of multiple lesions of various sizes, both without requiring removal of the delivery catheter from the patient. Such stents and stent delivery catheters should be capable of treating lesions of particularly long length and lesions in curved regions of a vessel, and should be highly flexible to conform to vessel shape and movement. Such stent delivery catheters should further be of minimal cross-sectional profile and should be highly flexible for endovascular positioning through tortuous vascular pathways. At least some of these objectives will be met by the present invention.